This is a very cool ambient advert which was launched recently. It is for Unicef and revolves around land mines. Hopefully you can see the pictures, but I will explain the concept.
Self-adhesive stickers were place on pavements etc and appeared invisible. The top side of the sticker was decorated to match the pavement, and was sticky obviously. The bottom side was decorated as a land mine with poignant information on land mines, and reminding the shopper that stood on the sticker that if it had been a real land mine, they wouldn't still be walking. The sticker then had a call to action aimed at getting people to the Unicef website to donate.
Really original idea that should have had a grand effect on the passers by as they attached themselves to the sticker.
Heres the link you need to pass this on: http://tinyurl.com/d7w6gw